This invention relates to a thermo-setting, polymerizable composition with a very high heat resistance after curing, and also to an organic material-based wiring board with a distinguished heat resistance, prepared from the composition.
There is a current tendency to use wiring boards of higher density in many industrial applications including computers, and consequently wiring boards with a distinguished heat resistance, which can be subjected to direct bonding with a soldering material at an elevated temperature of at least 300.degree. C. are required for loading a large number of LSI chips and chip carriers efficiently, where the heat resistance is an important problem to be solved, because of much heat generation due to the increase in the loading density.
Among the conventional wiring boards based on organic polymers, those based on aminobismaleimide-based polymer as disclosed in, for example, Japanese Patent Publication No. 47-42160 are most distinguished in the heat resistance, but their heat resistance are still unsatisfactory for the said industrial applications, and also for bonding with a metal for electro-conductive circuits.
To solve the problem, it is disclosed in Japanese Patent Publication No. 58-27665 to use a ceramic material having a distinguished heat resistance such as alumina, etc. as an insulating layer on the said wiring board on which LSI chips and chip carriers are directly loaded. However, the wiring board has a higher dielectric constant than that of the organic material, for example, 7-9, and thus has a limit in the signal propagation speed. Furthermore, the ceramic material has a dimensional shrinkage of 15-20% at the firing and thus has problems of locational discrepancy between the layers at the lamination, etc.
On the other hand, it is known that polymers having an isomelamine ring, obtained by reaction of a dicyanamide compound with a polymerizable compound of at least divalency, for example, a polyvalent imide having an unsaturated bond, a polyfunctional epoxy compound, an organic carboxylic acid having at least divalency, or its anhydride, has a good heat resistance [Japanese Patent Application Kokai (Laid-open) No. 58-79017].
As a result of further extensive studies of optimal conditions for producing the polymers having an isomelamine ring, that is, combinations, mixing ratio, physico-chemical characteristics of the starting compounds, the present inventors have found an effective thermo-setting, polymerizable composition for a wiring board and its insulating layer, which can be subjected to direct bonding of a large number of LSI chips, etc., and has a good bonding characteristic to an electroconductive circuit and an insulating layer, and a good heat resistance. The present invention is based on such finding.